Spinal cord injuries may arise from car accidents, violent crimes, falls and sports injuries. Spinal cord injury is a major neurological problem since most damage resulting from the injury is irreversible. Injured nerves fibers do not normally regenerate with resulting loss of nerve cell communication, leading to paralysis and loss of sensation.
After spinal cord severance, a new glial basal lamina forms to cover the exposed surface of the cord end regions. The glial cells also secrete barrier molecules that are difficult to penetrate, further suppressing reestablishment of nerve interconnections. The spinal cord tissue bordering the severed region becomes necrotic, detaches from the spinal cord, and develops irregular cavities.
Most tissue in the human body originates from undifferentiated cells known as stem cells. These fundamental building blocks differentiate into specific target parenchymal tissue based on hormonal and other local signals. Scientific evidence suggests that stem cells injected into a target tissue will differentiate into a cell line specific to the host tissue. This capability is of particular interest in treating conditions involving organs, such as the spinal cord, heart and brain that cannot regenerate.
Initial enthusiasm concerning stem cell implantation in patients was tempered by the ethical and logistic concerns of utilizing embryonic stem cells. Recent developments in stem cell research suggest adult stem cells can be harvested from the bone marrow and other tissues. Many such “cell lines” have been generated and are undergoing clinical evaluation. If successful, this work will obviate the moral and ethical dilemma of utilizing tissue from embryos for research.
Pressurized direct injection of certain bioactive agents, such as stem cells, is expected to inflict physical damage to the cell membranes due to fluid turbulence and pressure fluctuations (referred to herein as “barotrauma”) during the injection process. The damage may include lysis of the cells or injury to the cells that may significantly reduce the yield of viable cells delivered at the injection site and/or trauma to the target tissue. Forceful injection of any material into tissue also may disrupt the delicate intercellular matrix, thereby causing target tissue cellular injury.
In view of these drawbacks of previously known apparatus and methods, it would be desirable to provide methods and apparatus for treating severed or injured spinal cords by atraumatically delivering a bioactive agent, e.g., stem cells, within or adjacent to the injured spinal cord to promote nerve regeneration.
It would be also desirable to provide methods and apparatus for treating spinal cord injury by is delivering a bioactive agent so as to reduce the risk of barotrauma to the agent and target tissue during delivery.
It would be further desirable to provide apparatus and methods for treating spinal cord injury by delivering a bioactive agent to damaged tissue to promote tissue regeneration, wherein the apparatus and methods enhance the proportion of viable material delivered to the damaged tissue.
It further would be desirable to provide apparatus and methods for treating a spinal cord injury to cause nerve regeneration of both the sensory and motor nerves in the spinal cord.